The present invention relates to a method of determining the position of a transmitting beacon which transmits a signal to certain satellites in a constellation of satellites which, in turn, retransmit retransmitted signals to terrestrial detection stations.
When the terrestrial detection stations have directional receiver antennas pointed at the various satellites situated in the zone of visibility, then each retransmitted signal received is automatically associated with a satellite.
It is then possible to calculate the position of the transmitting beacon, in particular by the least squares method.
The drawback of such a method is that each ground station needs to be fitted with the same number of antennas as there are satellites whose signals are to be detected, and each antenna must also be provided with control apparatus suitable for ensuring that it tracks the satellite with which it is associated.
The invention seeks to simplify the ground installation by limiting the number of antennas.
For each ground station, the invention provides for implementing at least one, and preferably only one antenna suitable for receiving signals from a plurality of satellites situated in the visibility zone of that station.
Under such conditions, the retransmitted signals as received are no longer identified as coming from any particular satellite.
The idea on which the invention is based is to achieve such identification by computation.
The invention thus provides a method of using the least squares method to determine the position of a transmitting beacon transmitting a signal to certain satellites in a constellation of satellites, which satellites in turn retransmit retransmitted signals to at least one detection ground station, wherein at least one ground station is provided with at least one antenna, in particular an omnidirectional antenna, whose directional characteristics do not make it possible to identify which satellite retransmitted any given retransmitted signal, and wherein the method implements the following steps:
a) computing position for all combinations associating retransmitted signals received by said antenna with satellites of the constellation whose retransmitted signals are capable of being detected by said antenna;
b) computing the position of the beacon for at least some of the satellite combinations, using the least squares method; and
c) determining the combination which presents the smallest computation residue by the least squares method, the position of the transmitting beacon corresponding to this combination then being considered to be the position of the transmitting beacon.